Acute graft-versus-host disease (GVHD) is the primary limitation of allogeneic hematopoietic cell transplantation (HCT). There are currently no reliable diagnostic tests to predict the outcome of treatment, which correlate to long term survival. We have recently evaluated six previously validated diagnostic biomarkers of GVHD (IL2R?, TNFR1, HGF, IL8, elafin, and REG3?, for their ability to predict which patients would respond to therapy and who would achieve long term survival. We measured biomarker concentrations by from samples prospectively obtained at the initiation of treatment and day 28 following treatment in 112 patients who participated in a multicenter, randomized phase II clinical trial for newly diagnosed acute GVHD. We discovered an algorithm using values from all six biomarkers that predicted both day 28 response to treatment and mortality at day 180 from onset. This project will validate that algorithm by measuring all six biomarkers in a second group of 200 patients who patients who have recently participated in a multicenter, randomized phase II clinical trial for newly diagnosed acute GVHD. Awe will also develop a new algorithm by including a seventh biomarker that also predicts for response to treatment for GVHD. This algorithm will include both responses to treatment on day 28 after initiation of treatment as well as mortality at day 180 from the initiation of treatment.